Javascript_Methods_Asked_In_Interviews

tostring() Method:

toString() method converts an array to a string of array Values

//toString():

let arr = ["a","b","c","d","e"];
console.log("toString() : ", arr.toString());

join method()

join() method is same as toString() method, but we can specify a seprator also.It can be anything like ", / + -"

//join():

let arr1 = ["a","b","c","d","e"];
console.log("join() : ", arr.join("/"))

pop() method

pop() method removes the last element from an array.This method returns the value that was popped out.

//pop():

let arr2 = ["a","b","c","d","e"];
console.log(arr2.pop());  //returns the value that was popped out 
console.log(arr2);

push() method()

push() method add a new element in the array. This method returns the length of array

//push():

let arr3 = ["a","b","c","d","e"];
console.log(arr3.push("f"));
console.log(arr3);

shift() method

shift() method is same as pop(), but it removes the first element instead of last. This method returns the value that was shift out.

//shift():

let arr4 = ["a","b","c","d","e"];
console.log(arr4.shift());
console.log(arr4);

unshift() method

unshift() method is same a push(), but it adds a new element in the array at first This method returns the length of array.

//unshift():

let arr5 = ["a","b","c","d","e"];
console.log(arr5.unshift("f"));
console.log(arr5);

delete() method

Array elements can be deleted using javascript operator delete.This method returns true. Deleting elements leaves undefined holes in the array.

//delete():

let arr6 = ["a","b","c","d","e"];
console.log(delete arr6[0]);
console.log(arr6);

concat() method

concat() method returns a new array by merging existing array. This method does not change the existing array.It always returns a new array.

//concat():

let arr7 = ["a","b","c"];
let arr8 = ["d","e"];
console.log(arr7.concat(arr8));

splice() method

splice method is used to change the contents of an array by removing, replacing and adding new element at the specified index.

SYNTAX : array.splice(start, deleteCount, item1, item2, ...); This method returns the deleted elements.

//splice():

let arr9 = [ 'a', 'b', 'c', 'd' ];
let arrsplice = arr9.splice(1,2,"e","f");
console.log(arr9);
console.log(arrsplice);

slice() method

slice method extracts a section of an array into a new array.It does not modify the existing array.

SYNTAX : array.slice(start, end);

//slice():

let arr10 = [ 'a', 'b', 'c', 'd','e','f' ];
console.log(arr10.slice(1,4));

spread operator

spread operator expands an array into its individual elements.

//spread operator(...):

let arr11 = [ 'a', 'b', 'c', 'd' ];
console.log("spread operator",...arr11);

for of operator

This method iterates through the collection, and provides you the ability to modify specific items.

//for of operator():

let arr12 = [ 'a', 'b', 'c', 'd' ];
for(const item of arr12){
  console.log("for of operator",item) 
}

map() method

This method creates a new array with the result of calling a providing function on every elements in the array.

//map():

let arr13 = [1,2,3,4,5];
console.log(arr13.map(ele =>ele + 30));

filter() method

This method creates a new array with only elements that passes the condition inside the providing function.

//filter():

let arr14 = [1,2,3,4,5];
console.log(arr14.filter(ele => ele<=4));

sort() method

This method is used to sort array's element either in ascending or descending order.

//sort():

let arr15 = [4,2,5,1,3];
console.log(arr15.sort((a,b) => a>b ? 1:-1)); //ascending.
console.log(arr15.sort((a,b) => a>b ? -1:1)); //descending.

forEach() method

This method helps to loop over array by executing a provided callback function for each element in an array.

SYNTAX : array.forEach(callback(currentValue, index, array), thisArg);

//forEach():

let arr16 = [ 1, 2, 3, 4, 5 ];
arr16.forEach(ele => {
   console.log(ele);  
});

every() method

This method checks every element in the array that all elements passes the condition returns true or false.

//every():

let arr17 = [ 1, 2, 3, 4, 5 ];
console.log(arr17.every(ele => ele < 6));

includes() method

This method checks that the passes condition includes the elements or not, returning true or false.

//includes():

let arr18 = [ 1, 2, 3, 4, 5 ];
console.log(arr18.includes(4));

some() method

This method checks if atleast one element in the array that passes the condition returning true or false.

//some():

let arr19 = [ 1, 2, 3, 4, 5 ];
console.log(arr19.some(ele => ele >3));

reduce() method

This method applies a function against accumulator and each element in the array to reduce it to a given value.

//reduce():

let arr20 = [ 1, 2, 3, 4, 5 ];
console.log(arr20.reduce((acc,value) => acc+value));

find() method

This method returns the value of first element in the array that pass the test in the testing function

//find():

let arr21 = [ 1, 2, 3, 4, 5 ];
console.log(arr21.find(ele => ele < 4));

findIndex() method

This method returns the index of first element in the array that pass the test in the testing function.

//rindIndex():

let arr22 = [ 1, 2, 3, 4, 5 ];
console.log(arr22.findIndex(ele => ele < 4));

reverse() method

This method reverse an array in place. Elements in last index will be the first and vice-versa.

//reverse():

let arr23 = [ 1, 2, 3, 4, 5 ];
console.log(arr23.reverse());

ShubhamJoshi1998/Javascript_Methods_Asked_In_Interviews